This invention relates to silver halide material developing solutions.
There is a continuing need to provide new types of developing solutions as the commercial needs change. At the moment liquid concentrate developing solutions are finding greater favor than powder developers because they do not need dissolution and heating. That is to say, all the ingredients which are necessary to effect development of the exposed silver halide material are dissolved in an aqueous solution which is made as concentrated as possible. This solution is diluted with water to prepare a working strength solution.
Concentrated developing solutions are used in two ways. The first is as a single shot developer wherein the concentrated developing solution is diluted to the working strength developing solution and this solution is used once only. In this case the development is often carried out in a shallow dish or in a small spiral tank.
The other mode of use for concentrated liquid developing solutions is in deep-tank processing wherein the exposed photographic material is fed into and out of the tank. The concentrated developing solution is diluted to the correct strength either in or outside the tank with the requisite amount of water. An important requirement of this developing solution in the diluted form is that it should remain active over a long period. Often the activity of the developing solution in such tanks is maintained by the addition of some of the working strength developing solution, in such an amount so as to at least maintain the volume of the bath preferably in excess of this amount so as to maintain both the volume and the activity of the bath.
To provide a developing solution with a long life which yields developed image of low graininess, it is necessary to incorporate in the concentrated solution as much sulphite as possible.
In the past this has been achieved by the presence in the solution of an alkanolamine which is able to complex a large amount of sulphite as an alkanolamine sulphite/water mixed solution. Alkanolamines in the presence of sulphite form either alkanolamine sulphite or bisulphite. Diethanolamine (DEA) is a widely used alkanolamine. However, diethanolamine sulphite or bisulphite has a very high viscosity and it has been found difficult to formulate concentrated developers having a sufficiently high sulphite content. Further, alkanolamines and in particular diethanolamine tend to accelerate the process of chemical development. This causes a build-up of image density with a reduced contribution from physical development. This tends to produce an image which is more grainy than an image obtained in the absence of an alkanolamine.
Thus it is the object of the present invention to provide a liquid concentrate developer which when diluted has a long useful life but which produces developed images of low graininess.